1. Field of the Invention
The present invention relates to an antenna apparatus, and more specifically, relates to an antenna apparatus in which an antenna element comprising a conductive plate having a slot formed thereon is attached to a dielectric substrate.
2. Prior Art
There is an antenna apparatus having an antenna element having a straight-line notch (hereinafter referred to as a xe2x80x9cslotxe2x80x9d) formed on a conductive plate attached to a dielectric substrate (hereinafter referred to as a xe2x80x9cslot antennaxe2x80x9d). By feeding power to the slot of this antenna apparatus from a high frequency power source, the electromagnetic field resonates in the slot to thereby radiate radio wave. This kind of slot antenna has excellent electric characteristics, and hence is used in a wide range of application.
The above-described slot antenna, however, is suitable for being used as a single antenna, but it is difficult to use it as a polarization diversity antenna. It is also difficult to arrange a plurality of slot antennas, due to a restriction in the antenna size or the like. Moreover, by arranging a plurality of slot antennas on the space for one slot antenna, interference between antennas increases, and hence practical use of such an antenna has been difficult.
It is therefore a primary object of the present invention to provide a small and highly efficient antenna apparatus having a polarization diversity function with a plurality of antenna elements. A secondary object of the present invention is to provide an antenna apparatus having a broadband property.
In order to achieve the above objects, a first aspect of the present invention provides an antenna apparatus in which an antenna element comprising a conductive plate having a slot formed thereon is attached to a dielectric substrate, wherein the antenna element comprises: a conductive plate attached to one face of the dielectric substrate and having a cross-shaped slot formed thereon; a crossing area potential-relaxing conductive part attached at the position of a crossing of the cross-shaped slot on the other face of the dielectric substrate; and a strip-shaped radiation area potential-relaxing conductive parts attached at the position of a radiation area of the cross-shaped slot on the other face of the dielectric substrate.
A second aspect of the present invention provides an antenna apparatus in which an antenna element comprising a conductive plate having a slot formed thereon is attached to a dielectric substrate, wherein the antenna element comprises: a conductive plate attached to one face of the dielectric substrate and having a plurality of cross-shaped slots formed thereon; a crossing area potential-relaxing conductive part attached at the position of each crossing of each cross-shaped slot on the other face of the dielectric substrate; and a strip-shaped radiation area potential-relaxing conductive parts attached at the position of each radiation area of each cross-shaped slot on the other face of the dielectric substrate.
In addition to the above construction, the antenna apparatus of the present invention is preferably such that a reflecting plate consisting of a conductor is provided on the other face of the dielectric substrate, via spacers in parallel thereto, so as to cover the dielectric substrate.
In addition to the above construction, the antenna apparatus of the present invention is preferably such that an electric characteristics adjusting plate consisting of a conductor is provided on one face of the dielectric substrate, via spacers in parallel to the dielectric, so as to cover the central portion of each cross-shaped slot.
In addition to the above construction, the antenna apparatus of the present invention may have a notch formed on the electric characteristics adjusting plate.
In addition to the above construction, the electric characteristics adjusting plate of the antenna apparatus of the present invention may comprise another dielectric substrate, a main non-feeding element attached on the other dielectric substrate, and a plurality of strip-shaped sub non-feeding element attached in parallel to an opposing side of the main non-feeding element on the other dielectric substrate.
In addition to the above construction, a notch may be formed on at least either one of the main non-feeding element or the sub non-feeding element of the antenna apparatus of the present invention.
In addition to the above construction, in the antenna apparatus of the present invention, it is desired that power is fed in parallel to the radiation area of each slot.
According to the present invention, by feeding power to two radiation areas perpendicular to each other of the cross-shaped slot formed on the conductive plate, polarization diversity is performed. By forming a plurality of such cross-shaped slots on the conductive plate, attaching the crossing are a potential-relaxing conductive part on the backside of the crossing of each slot on the dielectric substrate and attaching the radiation area potential-relaxing conductive parts on the backside of the radiation area of each slot, a small and highly efficient antenna apparatus can be obtained. Also by providing the electric characteristics adjusting plate on one face of the dielectric, an antenna apparatus having a broadband property can be obtained.
According to the present invention, the following excellent effects can be exerted.
A plurality of antenna elements can realize a small and highly efficient antenna apparatus having a polarization diversity function, an antenna apparatus having a broadband property can be also provided.